Vesicular structures based on the phospholipid bilayer membrane are important vehicles for the storage and transport of biologically active agents in cellular systems. The object of this research is the investigation of the stability and permeability of synthetic lipid vesicles which mimic the fusion properties of the natural structures. Systems composed of phosphatidylcholine and one of several anionic lipids, including, phosphatidic acid and free fatty acids are under study. A variety of nuclear magnetic resonance (nmr) techniques are used to monitor species believed to be intimately involved in the fusion process. These techniques include spin relaxation time measurements and chemical shift measurements 31P, 19F, 1H and 13C sites either naturally occurring or synthetically incorporated in the species of interest. Loss or transfer of internal contents during fusion is monitored in a similar way. Gel permeation chromatography and differential scanning calorimetry are used to further characterize fused and unfused systems. It is hoped that data dealing with the redistribution of lipids and loss or retention of contents will elucidate the molecular nature of vesicle-membrane fusion. BIBLIOGRAPHIC REFERENCES: MPN Gent and JH Prestegard, "Interaction of the Polyene Antibiotics with Lipid Bilayer Vesicles Containing Cholesterol," Biochim Biophys Acta, 426, 17-30 (1976). MPN Gent and JH Prestegard, "19F Nuclear Magnetic Resonance Studies of Lipid Bilayer Systems," J. Am. Chem. Soc., 98, 3749 (1976).